This invention relates generally to microprocessor controlled television receivers and particularly to microprocessor controlled television receivers that include a keyboard and that are also remotely controllable.
The development of electronic tuning for television receivers not only significantly enhanced receiver performance and reliability, but also simplified viewer control of receiver tuning by enabling tuning by channel number. Electronic tuning systems for all practical purposes have even eliminated the need for fine tuning of the receiver. Such tuning systems use varactor diodes that change their capacitance as a function of applied voltage, which characteristic is conveniently controllable by means of digital control circuitry. With the widespread availability of low cost microprocessors, additional functions of the television receiver have been digitally controlled which has led to even greater versatility and substantial simplification in manufacturing. It also resulted in the viewer having a degree of control over the television receiver which has heretofore been unattainable.
With microprocessor circuitry and with digital control techniques, most television receiver functions may now be controlled at the receiver by the simple actuation of one or more buttons or keys. The keys are generally arranged in a format similar to that commonly used in calculators and portable computers, with the keys being designated by their corresponding functions. The keyboard is regularly "scanned", on a time-shared basis, by circuitry in the microprocessor which determines when a key has been actuated, correlates the actuated key with the desired control function and produces a corresponding output for carrying out that control function. Such a keyboard scanning technique is well known in the prior art and is exemplified in Zenith Television Receiver Model No. SZ2577.
Commensurate with the increase in local control exercisable by the viewer at the television receiver itself, giant strides have been taken in remote wireless control of basic receiver functions, such as channel selection, volume level, color level, tint, and receiver on/off. Over the years, wireless control hand units have been used with television receivers with a great deal of success. With the advent of integrated circuitry, the number of receiver functions that may be conveniently controlled from a remote point has increased while the size of the wireless control hand units has decreased. A few years ago hand-held control units included three or four buttons or keys for indicating a corresponding number of functions. Today, the hand-held control unit may include many buttons in a keyboard arrangement for activating a number of functions and for providing direct access to television channels.
In the Zenith model television receiver referred to above, an integrated circuit is provided in the hand-held control unit for energizing the circuitry when a key is actuated for determining the actuated key and for generating and transmitting an appropriate control signal. The control signal consists of coded bursts of infrared (IR) energy that are received by an appropriate IR receiver at the television set, detected and converted into a series or stream of binary bits. The series of bits is applied to an input of the microprocessor in which the actual decoding circuitry is resident. The decoding circuitry functions to correlate the desired control function with the particular stream of coded binary bits received and for initiating appropriate control circuitry.
In practice, reception of a coded IR signal from the remote keyboard and "decoding" thereof by the microprocessor overrides function control signals from the local keyboard and vice versa. The system is subject to error with codes being interrupted by noise and the like.
Further, the rapidly expanding use of digital circuits in television receivers, has placed an increased burden on the microprocessor and has significantly increased the complexity of needed software programming. As a result, constraints have been placed on the ability of the microprocessor for controlling local keyboard scanning and function control decoding.
There is, therefore, a need in the art for a simple, reliable microprocessor-based keyboard controlled television receiver that is also remotely controllable.